The present invention relates to a flat radiator.
In the present context, the term flat radiator is intended to mean radiators which are based on electric gas discharges, in particular are based on dielectric barrier gas discharges, with a sheet-like geometry, which emit electromagnetic radiation both in the invisible region, for example ultraviolet (UV) or infrared (IR) radiation, and also in the visible region, i.e. light. In the latter case, the term xe2x80x9cflat lampxe2x80x9d is also in widespread use. The light can also be generated by conversion of UV radiation by means of phosphors.
In the case of the flat radiators which are designed for dielectric barrier discharges, either the electrodes, which are usually in strip form, of at least one polarity (for unipolar operation) or all the electrodes, i.e. the electrodes of both polarities (for bipolar operation), are separated from the gas fill, which is used as discharge medium, by means of a dielectric layer (one-sided or two-sided dielectric barrier discharge). Electrodes of this type are also referred to below as xe2x80x9cdielectric electrodesxe2x80x9d for short.
The document WO98/43277 has already disclosed a flat radiator for the background illumination of liquid crystal displays (LCDs). This flat radiator has a baseplate, a cover plate and a frame, which are connected to one another in a gastight manner by means of solder to form a discharge vessel. Structures which are similar to conductor tracks function as electrodes in the interior of the discharge vessel, as lead-throughs in the lead-through region and as external power supply conductors in the outer region. The flat radiator is connected to a pulsed voltage source, which acts as an electrical power supply unit, via the power supply conductors.
The direct connection between flat radiator and supply unit, which is less suitable for flexible and automated manufacture of the system, represents a drawback.
It is an object of the present invention to provide an improved contact system for a flat radiator, which is used for connection to an electrical supply unit.
This object is achieved by the features of claim 1. Particularly advantageous configurations are given in the dependent claims which refer back to claim 1.
In addition, a flat radiator having the contact system according to the invention, in accordance with claims 9 to 13, and a system having a flat radiator of this type and an electrical supply unit in accordance with claim 14 are claimed.
The electrical contact system according to the invention comprises a contact part with a U-shaped section, an insulating body, on which the U-shaped section of the contact part is mounted, and a receptacle for the insulating body with the mounted contact part. The U-shaped section of the contact part has two side walls and a connecting wall which connects these two side walls, the outer side of the connecting wall forming a contact surface. The U-shaped section of the contact part partially engages around at least a partial region of the insulating body. The contact part also comprises a connection part for an electrical connection line. For its part, the receptacle comprises two plates or at least a partial region of two plates, which are arranged at a distance from one another and, at least in sections, parallel to one another, which is suitable for this purpose, as well as an electrical connection face, which is arranged on one of the two mutually facing surfaces of the two plates. The insulating body is arranged with the mounted contact part between the two plates, in such a manner that the contact surface of the contact part is in electrically conductive contact with the connection face of the receptacle.
To increase the compressive force between the contact surface of the contact part and the connection face of the receptacle, a spring element is preferably arranged between the insulating body and that side of the U-shaped section of the contact part which is at the rear with respect to the contact surface. To allow contact part and insulating body to press onto the two plates (plate partial regions) of the receptacle by means of the force of this spring element, it is expedient, at least during mounting, for the contact part to be fitted only relatively loosely onto the body. Before being fitted into the receptacle, the insulating body and the contact part mounted thereon are pressed together, counter to the spring force of the spring element, until both components can be inserted into the receptacle. After the insertion has taken place, the load on the compressed spring element can be relieved, and the latter can build up the compressive force mentioned above. The spring element may either be formed separately from the contact part, for example in the form of a coil spring, or may be integrated in the contact part, for example in the form of a spring tongue, optionally even in single-piece form.
To prevent the two components from unintentionally becoming detached from one another, it is advantageous to provide the relevant region of the insulating body with at least one latching lug, preferably with one or two latching lugs on each side wall of this region. Accordingly, one or, if appropriate, both of the side walls of the U-shaped section of the contact part is/are provided with corresponding apertures for the associated latching lugs of the insulating body to latch into.
A further advantage of the use of one or more spring elements in the manner described above consists in the fact that in this way it is possible to compensate for tolerances in the distance between the partial regions of the plates which form the receptacle. Specifically, the application of pressure and consequently contact-making between the contact surface of the contact part and the connection face of the receptacle is ensured over the spring excursion of the spring element.
To facilitate sliding mounting of the U-shaped contact part, it is also advantageous for the corresponding edges of the insulating body to be provided with a bevel.
To improve the contact, the contact surface of the contact part may be soldered to the connection face of the receptacle, for example by means of HF soldering. To assist the soldering operation, it may be of assistance for the contact surface to have at least one bore in which solder is deposited.
The contact system is preferably equipped with more than one contact part, specifically with the same number of contact parts as there are corresponding connection surfaces on the receptacle or as there are electrical connection lines provided. By way of example, for two connection lines two contact parts are mounted on an insulating body in the manner described above.
One or more of the contact systems according to the invention explained above are integrated in a narrow side of a flat radiator of the type described in the introduction. In this way it is also possible, for example, for a plurality of groups of electrodes to be actuated independently of one another within the flat radiator, instead of a single electrode system. Moreover, in particular for large flat radiators, for example those with a diagonal of 20 inches or more, it may be advantageous to use more than one group of electrodes. This is because in this way it is possible to make the electrical supply to large radiators modular, by ensuring the total electric power uptake with the aid of a plurality of relatively low-power ballasts, in which case each individual ballast supplies a group of electrodes provided for this purpose. This has the advantage, inter alia, that the electrical ballasts belonging to smaller flat radiators can be used for large flat radiators. For details in connection with flat radiators with groups of electrodes, reference should be made, in addition, to EP-A 0 926 705.
It is preferable for one or each contact system to be integrated in a flat radiator in such a manner that a receptacle for the corresponding contact system is formed by an associated part of baseplate and front plate which projects beyond the frame of the discharge vessel.
Typically, two electrodes or bus conductor tracks which connect a plurality of electrodes from the electrode system or, if appropriate, each group of electrodes are led to the outside from inside the discharge vessel. The end piece of each electrode or bus conductor track there serves as a connection face for the receptacle and is preferably matched to the shape of the contact surface of the contact part.
The insulating body on which the contact part or contact parts has/have been mounted is inserted in the partial region between baseplate and front plate which serves as a receptacle, in such a manner that the or each contact surface is arranged, in an electrically connecting manner, above the corresponding end piece, which serves as a connection face. It is preferable for the components of the contact system to be designed and dimensioned in such a manner that there is space for the entire contact system in the narrow side of the flat radiator within the receptacle provided for this purpose. This has the advantage that this narrow side of the flat radiator can be covered with a diaphragm to protect against contact or for esthetic reasons.
In addition, the entire illumination system also has at least one electrical ballast, which is/are connected to the corresponding connection parts of the (respective) contact system by means of electrical connection lines.